The present invention relates to the field of jet engines comprising an afterburner duct for reheating the gases emanating from the gas generator.
Jet engines with afterburners comprise, from upstream to downstream, a gas generator, consisting of a gas turbine engine, producing gases heated by combustion, an afterburner duct, and an exhaust nozzle for exhausting the gases into the atmosphere. The engine is usually of the double-flow type, with a central primary flow and a peripheral secondary flow.
The afterburner duct is provided with a liner made of a material which is resistant to the gas combustion temperature, said liner being suitably cooled. At the inlet of the duct, fuel injection means are arranged in the gas flow path, combined with means forming flame holders.
With reference to FIG. 1, the flame holder means 10 are in the form of radial arms which are arranged in a star pattern with respect to the engine axis and which pass through the two flow paths for the primary and secondary flows, said arms being connected to one another by elements in the form of annular sectors 9. With reference to FIG. 2, the integrally cast arms 100 in the form of gutters have a U- or V-shaped cross section which is open in the downstream direction so as to create a negative pressure region capable of stabilizing the combustion therein. In at least part of the flame holders 10, fuel injectors 130 are placed inside within the cavity formed between the walls, upstream and in the vicinity of the apex, together with air ventilation baffles 120. Air is bled from the secondary flow and distributed by the baffles 120 toward the injectors 130. In order to protect these elements, a protective heat shield 110 is placed as a covering over this part of the arm 100 containing the fuel injectors 130 and the ventilation baffle 120.
Traditionally, as represented in FIG. 2, the air ventilation baffle 120 is centered at its upper part and at its lower part in the cavity of the arm 100. It is held in a radial position via a tenon 5 on the base of the tube which passes through the protective heat shield 110 and thereby rotationally immobilizes the baffle 120 in the arm 100.
However, it is not desirable to weaken the heat shield 110 by piercing it in order to retain the air baffle 120. Specifically, the protective heat shield 110, which is generally made of CMC (ceramic matrix composite), is damaged by peening and delamination, something which is particularly detrimental during vibratory operation.
Similarly, piercing and machining operations performed on protective metal shields lead to a concentration of stresses, thereby reducing the efficiency and useful life of said shields.
It is also known practice to pierce the arm 100 at its lower end so as to introduce there the air ventilation baffle 120, which is fastened via a washer 16 welded to the lower end of the air ventilation baffle 120, outside the arm 100, as represented in FIG. 3.
This alternative is not satisfactory since it requires piercing the arm 100 and therefore entails all of the disadvantages mentioned above.